Counterbalancing mechanism for overhead track doors



April 17, 1951 s. o. SVENDSEN 2,549,140 COUNTERBALANCING MECHANISM FOR ovmmo TRACK DOORS Filed July 30, 1948 4 Sheets-Sheet l1 FIG.1.

Sidney Oliver .Svendseu. IN VEN TOR.

Aprll 17, 1951 V s. o. SVENDSEN 2,549,140

COUNTERBALANCING MECHANISM FOR OVERHEAD TRACK DOORS Flled July 50 1948 4 Sheets-Sheet 2 Sidney Oliver Sveridsen- INVENTOR.

April 17, 1951 s. o. SVENDSEN COUNTERBALANCING MECHANISM FOR OVERHEAD TRACK nooRs 4 Shasta-Sheet 3 Filed July 50, 1948 Sidney Oliver 5vendsen- INVEN TOR.

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April 17, 1951 Filed July 50, 1948 F1 qt, 6.

s. o. SVENDSEN COUNTERBALANCING MECHANISM FOR OVERHEAD TRACK DOORS 4 Sheets-Sheet 4 Sidney Oliver SvendseyG- INVENTOR.

Patented Apr. 17, 1951 COUN TERBALAN GIN G MECHANISM FOR OVERHEAD TRACK DOORS Sidney Oliver Svendsen, Birmingham, Mich., assignor to Glenn Berry, Birmingham, Mich.

Application July 30, 1948, Serial No. 41,698

This invention relates to a counterbalancing I mechanism for an overhead track door.

In an overhead track type of door the door is supported at each side and adjacent its top edge by rollers which roll in parallel horizontal tracks and in opening and closing this type of door the door also swings upon these rollers about a horizontal axis adjacent its upper edge. Thus, in traveling from a closed to fully open position, the door swings from a vertical to a horizontal plane and the swinging of the door is controlled by a pair of pivoted armspofsitioned along the opposite vertical edges of the door. In controlling the raising and lowering of the door, these arms are counterbalanced by coil springs and the load supported by these arms will depend upon the position of the door.

It is an object of this invention toprovide a clutch between the counterbalancing spring and each lever arm which will vary the leverage of the spring in accordance with the load imposed by the door upon the lever arm.

This object is accomplished by a clutch which shifts the point of application of the power of the spring to the lever arm away from its fulcrum to increase it leverage as the load increases and toward the lever fulcrum to decrease its leverage as the load decreases.

In the drawings:

Fig. 1 is an inside elevation showing my counterbalancing mechanism and overhead track door in closed position.

Fig. 2 is an inside elevation showing the same in partially and fully raised positions.

Fig. 3 is a rear elevation showing my counterbalancing mechanism with the door in lowered position and the casing for the counterbalancing mechanism broken away.

Fig. 4 is a vertical section along the line 44 of Fig. 3.

Fig. 5 is an enlarged detail section showing in the full lines the position of my counterbalancing mechanism when the door is half raised (dotted line showing Fig. 2) and showing in the dotted lines the position of my counterbalancing mechanism when the door is fully raised (full line showing Fig. 2).-

Fig. 6 is a section along the line 6-6 of Fig. 4. Referring more particularly to the drawings,

I have'shown a door I supported upon shafts 2 mounted in rollers 3 which in turn are supported upon and arranged to travel back and forth in the fixed overhead channel tracks 4.

For controlling the movement of the door from closed to raised position and vice versa, I provide a pair of lever arms 5. Eachlever arm 5 has one end pivotally secured to the door adjacent its bottom edge by means of pin 5 and the other end of each lever is afiixed to a horizontal shaft I (Fig. 6) journalled in spaced bearings 8 and 9 mounted in sheet metal housing I0. Each 6 Claims. (01. 16-1) housing I0 is secured in an upright position to the door jamb II by screws I2. Shaft I' has a crank arm I3 fixed thereto. Headed pins I4 and I 5 are fixed to crank arm I 3 and engage a clutch plate I6 in a T slot I'I comprising arcuate cross portion I8 and arcuate stem portion I9. It will be noted that pin I4 is positioned a greater radial distance from shaft 1 than pin I5. A helical coil counterbalancing tension spring 2!] has one end anchored as at 2| to the lower end of clutch plate I5 and the other end anchored to bolt 22 which is fixed to the base 23 of housing Ill.

The operation of my counterbalancing spring is as follows: As shown in Figs. 1, 3, 4 and 6, the door I is closed, arm 5 is substantially parallel to the plane of the door and the tension or power of spring 26 is applied through clutch plate It to pin [5 on crank arm I 3. Crank arm I3 is parallel to lever arm 5 and in effect forms an offset extension of lever arm 5. Thus, as a practical matter, crank arm I3 and arm 5 form a lever which has its fulcrum or pivot on shaft 1. As illustrated in Fig. 4, the door I is in lowered position and spring 20 applies its power on pin I5 slightly over center or to the right of shaft I so that the spring is tending to hold door I closed. In other words, a line drawn through the center of pin I5 and bolt 22 will pass slightly to the right of the center of shaft I, Fig. 4. However, if desired, spring 20, when the door is lowered, can apply its power directly on center.

To open the door one grasp the lower edge of the same and pulls outwardly. This causes lever arms 5 to swing counterclockwise about shafts I, as viewed in Figs. 4 and 5. As the arms 5 swing upwardly in a counterclockwise direction, the power of spring 20 is applied through pin. I5 to crank arm I3 and pin I4 idles in slot I 9 and travels outwardly from cross slot I8 until lever arm 5 reaches approximately horizontal position, Fig. 5. The door at this time will be approximately half raised, Fig. 2. Note that as the lower edgeof the door swings outwardly, the upper edge travels inwardly supported by rollers in tracks 4. As the lever arm 5 swings from lowered position, Fig. 4, to horizontal position, Fig. 5, the effective length of the lever arm between pin I5 and shaft 1 gradually increases and thereby increases the leverage of spring Never the door I. As lever arm 5 swings from the horizontal position, pin I 5 begins to travel downwardly and toward the right so that it approaches a vertical plane passing through shaft 1 and therefore the effective length of the lever arm between pin I5 and shaft 1 gradually decreases. In other words, if spring Ell applied its power to spring l5 from the position shown in Fig. 5 until arm 5 reaches vertical. position, then spring 20 would be losing leverage or mechanical advantage. However, when the door reaches half-way position and lever arm 5 is substantially horizontal, clutch plate I'6 shifts the power of spring 20 from pin IE) to pin I4 which not only maintains the mechanical advantage or 1everage of spring '2!) but gradually increases the same until pin M reaches a horizontal plane passing through shaft 1. A pin I' l travels below wardly in cross slot 13 until at fully raised position pins [4 and I5 are now at the extreme upper ends of their respective slots I9 and [8 but the power of spring 2!] is still applied through pin I4.

Upon lowering the door arm 5 will pass from vertical position, dotted line showing, Fig. 5, clockwise to the horizontal position and then to the lowered vertical position, Fig. 4. In passing from the dotted line position, Fig. 5, clockwise to the full line position, spring 20 applies its power through pin it to lever arm IS with increasing mechanical advantage and at midway or horizontal position of crank arm i3 and lever 5, clutch plate it again shifts the power of spring 20 over to pin I5 because at this point pin it begins to rapidly lose leverage. As lever 5 swings down, the tension or power of spring 26 increases'reaching it maximum tension at fully lowered position and the reverse of this occurs as thedool' is raised; namely, the tension or power of spring 20 decreases and reaches its minimum at the fully raised position of the door. Thus, clutch l6 cooperates with pins i i and 15 to compensate for the changing power or tension of spring 20 and also to compensate for the varying mechanical advantag or leverage exerted by the load or weight of the door on arm 5.

The net effect of my clutch arrangement is that when the door is in half raised position and a substantial distance above and below half raised position, the door will be exerting maximum torque upon shaft l and therefore spring 20 needs to have a maximum leverage or mechanical advantage which is provided by the clutch which shifts the power from pin iii to i l on the way up and from M to IE on the way down. In raised and lowered position of the door the torque applied upon shaft 1 is practically nil because the load on lever 5 exerts a thrust directly against shaft 1 rather than torque or turning motion.

From the above it is evident that I have provided a simple counterbalancing mechanism which aids the operator in raising and lowering the door with a minimum of effort because the spring as it loses tension increases its effective lifting power, leverage or counter torque on shaft 1 as the load or door increases its torque or turning component on shaft 1, and vice versa.

I claim: V

l. Counterbalancing mechanism adapted for use with a door of the overhead track type comprising in combination a lever of the first order having a load arm and a power arm on opposite sides of its fulcrum, the load arm of said lever being adapted to support the door, counterbalancing power means for the power arm of said lever, a shiftable transmission for connecting the power arm to the counterbalancing power means, said shiftable transmission comprising a pair of pins on said power arm spaced unequally from the fulcrum of said lever and an anchoring member on said counterbalancing means pivotally engageable with one of said pins during a portion of the pivo tal movement of said lever and with the other 4 pin during the remainder of said pivotal movement, said shiftable transmission increasing the effective length of the power arm of the lever through a distance of more than half its pivotal movement as the force exerted by the counterbalancing power means upon the power arm decreases and decreasing the effective length of the power arm through a distance of over half its pivotal movement as the force exerted by the counterbalancing power means on the power arm increases.

2. The combination as set forth in claim 1 wherein the lever swings through an arc of substantially as the door moves from closed to fully open position and the power means exerts its maximum force upon the power arm when the door is lowered and its minimum force upon the power arm when the door is raised.

3. The combination as set forth in claim 2 wherein the lever is mounted upon a horizontal axis and the power arm swings from a position vertically below the fulcrum to a position vertically above the fulcrum, said pins being positioned such that the force is applied substantially upon dead center when the lever is in fully raised or fully lowered position. 7

4. Counterbal'ancing mechanism adapted for use with a door of the overhead track type comprising in combination a lever of the first order having a load arm and a power arm, the load arm being adapted for connection to the door, count'erbalancing means, a variable-transmission between the power counterbalancing means and the power arm of the lever comprising a member having a T slot therein and a pair of spaced pins adapted to travel in said T slot, one pin being positioned a greater radial distance from the fulcrum than the other pin, the pin closest to the fulcrum being adapted to travel in the cross member of the T slot and the pin member the greatest distance from the fulcrum being adapted to travel in the stem of said T slot, the said power counterbalancing means exerting its greatest force on the power arm when the lever is in one of its extreme positions, and a minimum force when the lever arm is in the other of its extreme positions, the pin closest to the fulcrum applying the force to the power arm when the counterbalancing power means is exerting its maximum power and the other pin transmitting the force to the power arm when the power means is exerting its minimum force.

'5. The combination as set forth in claim 4.- wherein the cross member of the T slot is an are connected with one end of the stem of the T and having its center at the opposite end of the stem of the T and the stem of the T slot is an are having its center at the end of the cross bar of the T below the end of the stem.

6. The combination as set forth in claim 5 wherein the counterbalancing power means is a tension spring the lower end of which is anchored substantially vertically below the fulcrum.

SIDNEY OLIVER SVENDSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Deuring Aug. 1'7, 1943 

